Patient hydration system and method

ABSTRACT

A fluid management system for a patient includes a console for mounting on an IV pole. The console includes an input for setting a desired fluid balance for a set therapy duration. A weighing subsystem weighs the patient&#39;s urine output collected in a urine collection chamber and weighs a source of hydration fluid. An infusion pump is integrated with the console and is configured to pump hydration fluid from the source of hydration fluid into the patient. A controller in the console is responsive to the set desired fluid balance, the set therapy duration, and the weighing subsystem. The controller is configured to determine the patient&#39;s urine output based on the weight of the urine collection chamber, determine the amount of fluid infused into the patient, and control the infusion pump to inject hydration fluid into the patient based on the set desired fluid balance, the weight of the urine collection chamber, and the weight of the source of hydration fluid to achieve the desired fluid balance during the set therapy duration.

RELATED APPLICATIONS

This application is a divisional of prior U.S. patent application Ser.No. 10/936,945 filed Sep. 9, 2004, which is incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to a patient hydration system and method whereinthe rate of hydration fluid delivered to the patient is automaticallyadjusted based on the urine output of the patient to maintain, asnecessary, a zero, positive, or negative net fluid balance in thepatient.

BACKGROUND OF THE INVENTION

There are many medical procedures in which proper hydration of thepatient is critical. For example, it has been observed that dehydrationincreases the risk of radiocontrast nephropathy (RCN) when radiocontrastagents are injected into a patient during coronary and peripheralvascular catheterization procedures. RCN is the third most common causeof hospital-acquired renal failure. It occurs in over 5% of patientswith any baseline renal insufficiency and in 50% of patients withpreexisting chronic renal insufficiency and diabetes. Radiocontrastmedia has a variety of physiologic effects believed to contribute to thedevelopment of RCN. One of the main contributors is renal medullaryischemia, which results from a severe, radiocontrast-induced reductionin renal/intrarenal blood flow and oxygen delivery. The medullaryischemia induces ischemia and/or death of the metabolically active areasof the medulla responsible for urine formation, called the renaltubules. Medullary ischemia is attributed to the increase of oxygendemand by the kidney struggling to remove the radiocontrast media fromblood plasma and excrete it from the body at the same time as the normalprocess of controlling the concentration of urine. Oxygen consumption inthe medulla of the kidney is directly related to the work ofconcentrating urine. Since the presence of radiocontrast media in theurine makes it much more difficult for the kidney to concentrate urine,the work of the medulla outstrips the available oxygen supply and leadsto medullary ischemia.

Although the exact mechanisms of RCN remain unknown, it has beenconsistently observed that patients with high urine output are lessvulnerable to contrast injury. It is also clear that dehydrationincreases the risk of RCN, likely because urine (and contrast mediainside the kidney) is excessively concentrated. As a result, patientspredisposed to RCN are hydrated via intravenous infusion of normalsaline before, during and after the angiographic procedure. Hydration iscommonly performed at a conservative rate, especially in patients withexisting heart and kidney dysfunction, since over-hydration can resultin pulmonary edema (fluid in the lungs), shortness of breath, the needfor intubation, and even death. Thus, the patients at highest risk forRCN are those least likely to receive the only proven therapy forpreventing RCN (I.V. hydration) due to the unpredictability of sideeffects from I.V. hydration.

A major limitation to the more widespread use of the already knowntherapeutic, or optimal, levels of I.V. hydration is the currentinability to balance the amount of fluid going into the patient to theamount of fluid being removed or excreted from the patient. It ispossible to have a nurse measure a patient's urine output frequently butthis method is impractical as nurses are often responsible for the careof many patients. In addition, the only accurate method of measuringurine output is to place a catheter into the patient's urinary bladder.Without a catheter, the patient must excrete the urine that may havebeen stored in the bladder for several hours. During this time, theamount of I.V. hydration can be significantly less than the amount ofurine produced by the kidneys and stored in the bladder, leading todehydration. Since patients do not normally have such a catheter duringprocedures using radiocontrast media, a valid measurement of urineoutput is not possible.

There seems to be indisputable scientific evidence that RCN in patientswith even mild baseline renal insufficiency can lead to long termcomplications and even increased risk of mortality. This scientificknowledge has not yet been extended to daily clinical practice asroutine monitoring of renal function post-catheterization is notperformed and limits the identification of the known short-term clinicalcomplications.

At the same time, there is a great deal of awareness in clinicalpractice that patients with serious renal insufficiency (serumcreatinine (Cr)≧2.0) often suffer serious and immediate damage fromcontrast. Many cardiologists go considerable length to protect thesepatients including slow, overnight hydration (an extra admission day),administration of marginally effective but expensive drugs, or even notperforming procedures at all.

There are approximately 1 million inpatient and 2 million outpatientangiography and angioplasty procedures performed in the U.S. per year(based on 2001 data). Based on the largest and most representativepublished studies of RCN available to us (such as Mayo Clinic PCIregistry of 7,586 patients) we believe that 4% of patients have seriousrenal insufficiency (Cr≧2.0). This results in the initial marketpotential of 40 to 120 thousand cases per year from interventionalcardiology alone. There is also a significant potential contributionfrom peripheral vascular procedures, CT scans and biventricularpacemaker leads placement. As the awareness of the RCN increases, themarket can be expected to increase to 10% or more of all cases involvingcontrast.

According to the prior art, hydration therapy is given intravenously(I.V.) when someone is losing necessary fluids at a rate faster thanthey are retaining fluids. By giving the hydration therapy with an I.V.,the patient receives the necessary fluids much faster than by drinkingthem. Also, dehydration can be heightened by hyperemesis (vomiting),therefore the I.V. method eliminates the need to take fluids orally. Ananesthetized or sedated patient may not be able to drink. Hydration isused in clinical environments such as surgery, ICU, cathlab, oncologycenter and many others. At this time, hydration therapy is performedusing inflatable pressure bags and/or I.V. pumps. A number of I.V. pumpson the market are designed for rapid infusion of fluids (as opposed toslow I.V. drug delivery) for perioperative hydration during surgery, ICUuse and even emergency use for fluid resuscitation.

An infusion pump is a device used in a health care facility to pumpfluids into a patient in a controlled manner. The device may use apiston pump, a roller pump, or a peristaltic pump and may be poweredelectrically or mechanically. The device may also operate using aconstant force to propel the fluid through a narrow tube, whichdetermines the flow rate. The device may include means to detect a faultcondition, such as air in, or blockage of, the infusion line and toactivate an alarm.

An example of a device for rapid infusion of fluids is the InfusionDynamics (Plymouth Meeting, Pa.) Power Infuser. The Power Infuser usestwo alternating syringes as a pumping engine. Since it is only intendedto deliver fluids (not medication), the Power Infuser has accuracy of15%. It provides a convenient way to deliver colloid as well ascrystalloid for hydration during the perioperative period among otherpossible clinical settings. The Power Infuser provides anesthesiologistswith the ability to infuse at rates similar to that seen with pressurebags, but with more exact volume control. The maximum infusion rate is 6L/hr. It has the flexibility of infusing fluid at 0.2, 1, 2, 4 and 6L/hr. A bolus setting of 250 mL will deliver that volume in 2.5 min. Ina large blood loss surgical case, the use of Power Infuser enables largevolumes of colloid to be delivered to restore hemodynamics.

It is also known in the art that loop diuretics such as furosemide(frusemide) reduce sodium reabsorption and consequentially reduce oxygenconsumption of the kidney. They also reduce concentration of contrastagents in the urine-collecting cavities of the kidney. They inducediuresis (e.g., patient produces large quantities of very dilute urine)and help remove contrast out of the kidney faster. Theoretically, theyshould be the first line of defense against RCN. In fact, they were usedto prevent RCN based on this assumption until clinical evidencesuggested that they were actually deleterious. More recently, doubtshave been raised regarding the validity of those negative clinicalstudies.

In two clinical studies by Solomon R., Werner C, Mann D. et al. “Effectsof saline, mannitol, and furosemide to prevent acute decreases in renalfunction induced by radiocontrast agents”, N Engl J Med, 1994;331:1416-1420 and by Weinstein J. M., Heyman S., Brezis M. “Potentialdeleterious effect of furosemide in radiocontrast nephropathy”, Nephron1992; 62:413-415, as compared with hydration protocol, hydrationsupplemented with furosemide adversely affected kidney function inhigh-risk patients given contrast. Weinstein et al. found thatfurosemide-treated subjects lost 0.7 kg on average, whereas a 1.3-kgweight gain was noted in patients randomized to hydration alone,suggesting that in furosemide-treated subjects the hydration protocolhas been insufficient and patients were dehydrated by excessivediuresis.

The clinical problem is simple to understand: diuresis is widelyvariable and unpredictable but the fluid replacement (hydration) at aconstant infusion rate is prescribed in advance. To avoid the risk ofpulmonary edema, fluid is typically given conservatively at 1 ml/hr perkg of body weight. The actual effect of diuretic is typically not knownfor 4 hours (until the sufficient amount of urine is collected andmeasured) and it is too late and too difficult to correct any imbalance.Meanwhile, patients could be losing fluid at 500 ml/hour while receivingthe replacement at only 70 ml/hour. The effects of forced diuresiswithout balancing are illustrated in the research paper by Wakelkamp et.al. “The Influence of Drug input rate on the development of tolerance tofurosemide” Br J. Clin. Pharmacol. 1998; 46: 479-487. In that study,diuresis and natriuresis curves were generated by infusing 10 mg of I.V.furosemide over 10 min to human volunteers. From that paper it can beseen that a patient can lose 1,300 ml of urine within 8 hours followingthe administration of this potent diuretic. Standard unbalanced I.V.hydration at 75 ml/h will only replace 600 ml in 8 hours. As a resultthe patient can lose “net” 700 ml of body fluid and become dehydrated.If such patient is vulnerable to renal insult, they can suffer kidneydamage.

To illustrate the concept further, the effects of diuretic therapy onRCN were recently again investigated in the PRINCE study by Stevens etal. in “A Prospective Randomized Trial of Prevention Measures inPatients at High Risk for Contrast Nephropathy, Results of the PRINCE.Study” JACC Vol. 33, No. 2, 1999 February 1999:403-11. This studydemonstrated that the induction of a forced diuresis while attempting tohold the intravascular volume in a constant state with replacement ofurinary losses provided a modest protective benefit againstcontrast-induced renal injury, and importantly, independent of baselinerenal function. This is particularly true if mean urine flow rates wereabove 150 ml/h. Forced diuresis was induced with intravenouscrystalloid, furosemide, and mannitol beginning at the start ofangiography.

The PRINCE study showed that, in contrast to the Weinstein study, forceddiuresis could be beneficial to RCN patients if the intravascular volumewas held in a constant state (no dehydration). Unfortunately, there arecurrently no practical ways of achieving this in a clinical settingsince in response to the diuretic infusion the patient's urine outputchanges rapidly and unpredictably. In the absence of special equipment,it requires a nurse to calculate urine output every 15-30 minutes andre-adjust the I.V. infusion rate accordingly. While this can be achievedin experimental setting, this method is not possible in current clinicalpractice where nursing time is very limited and one nurse is oftenresponsible for monitoring the care of up to ten patients. In addition,frequent adjustments and measurements of this kind often result in ahuman error.

Forced hydration and forced diuresis are known art that has beenpracticed for a long time using a variety of drugs and equipment. Thereis a clear clinical need for new methods and devices that will make thistherapy accurate, simple to use and safe.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a patienthydration system and method.

It is a further object of this invention to provide such a system andmethod which prevents kidney damage in a patient.

It is a further object of this invention to provide such a system andmethod which protects the patient undergoing a medical procedureinvolving a radiocontrast agent from kidney damage.

It is a further object of this invention to provide such a system andmethod which incorporates a balancing feature intended to preventdehydration, overhydration, and to maintain a proper intravascularvolume.

It is a further object of this invention to provide a balanced diuresismethod which automatically balances fluid loss in the urine.

It is a further object of this invention to provide such a system andmethod which is accurate, easy to implement, and simple to operate.

It is a further object of this invention to provide such a system andmethod which is particularly useful in the clinical setting of forceddiuresis with drugs known as I.V. loop diuretics.

The invention results from the realization that radiocontrastnephropathy in particular and patient dehydration in general can beprevented by automatically measuring the urine output of the patient andadjusting the rate of delivery of a hydration fluid to the patient toachieve, as necessary, a zero, positive, or negative net fluid balancein the patient.

This invention features, in one aspect, a fluid management system for apatient. The system typically includes a console for mounting on an IVpole. The console includes an input for setting a desired fluid balancefor a set therapy duration. A first attachment mechanism extends fromthe console for hanging a urine collection chamber. A second attachmentmechanism extends from the console for hanging a source of hydrationfluid. A weighing subsystem in the console is responsive to the firstattachment mechanism for weighing the patient's urine output collectedin the urine collection chamber and is responsive to the secondattachment mechanism for weighing the source of hydration fluid. Aninfusion pump is integrated with the console and configured to pumphydration fluid from the source of hydration fluid into the patient. Acontroller in the console is responsive to the set desired fluidbalance, the set therapy duration, and the weighing subsystem. Thecontroller is configured to determine the patient's urine output basedon the weight of the urine collection chamber, determine the amount offluid infused into the patient, and control the infusion pump to injecthydration fluid into the patient based on the set desired fluid balance,the weight of the urine collection chamber, and the weight of the sourceof hydration fluid to achieve the desired fluid balance during the settherapy duration.

In one embodiment, the console may include a display which displays theelapsed time of the therapy duration and the current fluid balance. Thesystem may include means for indicating, on the console, when the urinecollection is empty. The system may include means for indicating, on theconsole, when the source of hydration fluid is low on fluid. Thecontroller may be configured to determine the patient's urine outputbased on the rate of change of the weight of the urine collectionchamber, calculate a desired infusion rate based on the determined rateof change of the weight of the urine collection chamber and the setdesired fluid balance, and control the infusion pump to hydrate thepatient based at least on the calculated desired infusion rate.

This invention also features a fluid management system including aconsole which includes an input for setting a desired fluid balance, aurine collection chamber, a weighing device for weighing the patient'surine output collected in the urine collection chamber, a source ofhydration fluid, a pump associated with the console and configured topump hydration fluid form the source of hydration fluid into thepatient, and a controller in the console configured to: determine thepatient's urine output based on the weight of the urine collectionchamber, operate the pump, monitor the amount of hydration fluidinjected into the patient based, and control the pump based on the setdesired fluid balance, the amount of hydration fluid injected into thepatient, and the determined patient urine output.

This invention also features a fluid management system for a patientincluding a console for mounting on an IV pole. The console includes aninput for setting a desired fluid balance, a first attachment mechanismextends from the console for handing a urine collection chamber. Aweighing device in the console is responsive to the first attachmentmechanism for weighing the patient's urine output collected in the urinecollection chamber. A controllable infusion pump is integrated with theconsole and configured to pump hydration fluid from a source ofhydration fluid into the patient at a variable rate. A controller in theconsole is responsive to the set desired fluid balance and the weighingdevice. The controller is configured to determine the patient's urineoutput based on the rate of change of the weight of the urine collectionchamber, calculate a desired infusion rate based on the determined rateof change of the weight of the urine collection chamber and the setdesired fluid balance, and control the infusion pump to hydrate thepatient based at least on the calculated desired infusion rate.

This invention further features a method of addressing contrast inducednephropathy. One method includes injecting a contrast agent into apatient, imaging the patient, and including diuresis to drive anycontrast agent through the patient's kidneys to reduce its toxic effectson the kidneys and prevent damage to the kidneys. A desired fluidbalance is set. Urine expelled by the patient is collected in a urinecollection bag. The method typically includes weighing the urinecollection bag, employing a pump to infuse the patient with fluid from afluid source, weighing the fluid source, and automatically adjusting thepump based on the weight of the urine collection bag and the weight ofthe fluid source and controlling the amount of fluid infused into thepatient based on the amount of urine expelled by the patient and the setdesired fluid balance.

In another embodiment, the method may include the step of administeringa diuretic to the patient. Collecting urine expelled by the patient mayinclude catheterizing the patient. Catheterizing the patient may includeinserting a urinary catheter in the urinary tract of the patient.Weighing the urine collection bag may include providing an indicationwhen a urine collection bag has reached its capacity. The method mayfurther include providing an indication when the fluid source is low onfluid.

The subject invention, however, in other embodiments, need not achieveall these objectives and the claims hereof should not be limited tostructures or methods capable of achieving these objectives.

This invention also features a method of addressing contrast inducednephropathy for a patient who has had a contrast agent injected into thepatient. The method includes collecting urine expelled by the patient,determining the amount of urine expelled by the patient based on thecollected urine, infusing the patient with fluid from a fluid source,determining the amount of fluid infused into the patient, and inducingdieresis to dilute the concentration of any contrast agent in thepatient by automatically adjusting the amount of fluid infused into thepatient from the fluid source based on the determined amount of urineexpelled by the patient to balance the amount of urine expelled by thepatient with the amount of fluid infused into the patient.

This invention also features a method of driving a toxin through apatient's kidneys, the method including collecting urine expelled by thepatient. The method includes determining the amount of urine expelled bythe patient based on the collected urine, infusing the patient withfluid from a fluid source, determining the amount of fluid infused intothe patient, and inducing diuresis by automatically adjusting the amountof fluid infused into the patient from the fluid source on thedetermined amount of urine expelled by the patient to balance the amountof urine expelled by the patient with the amount of fluid infused intothe patient.

This invention also features a method of preventing kidney damage due todehydration, the method including collecting urine expelled by thepatient. The method includes determining the amount of urine expelled bythe patient based on the collected urine, infusing the patient withfluid from a fluid source, determining the amount of fluid infused intothe patient, and maintaining the patient's hydration level byautomatically adjusting the amount of fluid infused into the patientfrom the fluid source based on the determined amount of urine expelledby the patient to balance the amount of urine expelled by the patientwith the amount of fluid infused into the patient, increasing thepatient's level of hydration by infusing additional fluid based on usersettings over and above fluid infused to match the patient's urineoutput.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a schematic view of an example of a patient hydration systemin accordance with the subject invention;

FIG. 2 is a schematic view of one embodiment of a patient hydrationsystem in accordance with the subject invention wherein the weight ofthe urine output by a patient is measured and used as an input tocontrol the infusion rate of an infusion pump;

FIG. 3 is a schematic view of another embodiment of a patient hydrationsystem in accordance with the subject invention wherein the controllerand weighing mechanism are integrated in a single control subsystemunit;

FIG. 4 is a flow chart depicting one example of the software associatedwith the controller of this invention and the method of adjusting theinfusion rate based on the amount of urine output by the patient; and

FIG. 5 is a schematic view showing another embodiment of the subjectinvention wherein a flow meter is used to determine the amount of urineoutput by the patient.

DISCLOSURE OF THE PREFERRED EMBODIMENT

Aside from the preferred embodiment or embodiments disclosed below, thisinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Thus, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. If only oneembodiment is described herein, the claims hereof are not to be limitedto that embodiment. Moreover, the claims hereof are not to be readrestrictively unless there is clear and convincing evidence manifestinga certain exclusion, restriction, or disclaimer.

Patient hydration system 10, FIG. 1 according to this invention includesurine collection system 12 connected to patient P. Infusion system 20typically includes an infusion device such as infusion pump 22 (e.g., aperistaltic pump) connected to source 24 of infusion fluid 26 (e.g.,saline) by tubing 28. I.V. needle 30 is inserted in a vein of patient Pand is connected to infusion pump 22 via tubing 32.

A control system or hydration balance means 34 detects the amount ofurine output by the patient and automatically adjusts the infusion rateof infusion pump 22 to achieve, as necessary, a zero, positive, ornegative net fluid balance in the patient. Typically, urine collectionsystem 12 includes catheter 14 (e.g., a Foley catheter) placed in thebladder B of patient P. Tubing 16 connects catheter 14 to meter 36.Controller 38, typically programmable, is responsive to the output ofmeter 36 and is configured to adjust the infusion rate of infusion pump22.

In one example, meter 36, FIG. 1 is a weight measurement device such asscale 50, FIG. 2. Here, urine collection chamber 52 on scale 50 isconnected to catheter 14 via tubing 16. Scale 50 outputs a signalcorresponding to the weight of urine or the combined weight of urine andhydration fluid (in this case to maintain net-zero hydration, the scalereading should be maintained constant) or the difference between theweight of urine and the weight of hydration fluid in collection chamber52 to controller 38. The patient hydration system of this invention mayfurther include diuretic administration system 60 including a source 62of a diuretic such as furosemide administered via I.V. 64 inserted inpatient P and connected to source 62 via tubing 66. In alternativeembodiment, tubing 66 can be connected to the patient P via hydrationI.V. 30 using standard clinical techniques. Also, if desired, a urinepump such as, for example, peristaltic pump 70 can be used to urge urinefrom bladder B to collection chamber 52 and to automatically flushcatheter 14 if it is occluded. The advantage of urine collection pump 70is that collection chamber or bag 52 can be at any height relative tothe patient P. As shown, chamber 24 containing the hydration fluid 26can also be placed on scale 50 in an embodiment where differentialweighing is used. The controller (38) electronics and software arecapable of integrating urine output (for example every 15 or 30 minutes)and changing the infusion rate setting of the infusion pump 22 followingan algorithm executed by the controller.

Electronic controller 22 may also incorporate a more advanced featureallowing the physician to set a desired (for example positive) hydrationnet goal. For example, the physician may set the controller to achievepositive net gain of 400 ml in 4 hours. Controller 38 calculates thetrajectory and adjust the infusion pump flow rate setting to exceed theurine output accordingly. For example, to achieve a positive net gain of400 ml over 4 hour, controller 38 may infuse additional 25 ml ofhydration fluid every 15 minutes in addition to the volume of urine madeby the patient in each 15 minute interval.

In the embodiment of FIG. 3, the programmable controller and theweighing mechanism are integrated in controller unit 34″. The patient(See FIG. 1) is placed on the hospital bed or operating table 80. Thehydration I.V. 30 and the urinary collection (Foley) catheter 14 areinserted using standard methods. The controller electronics and theinfusion pump 22′ are integrated in the single enclosure of the controlsubsystem 34″ console 82. Console 82 is mounted on I.V. pole 84.

Control subsystem 34″ may also include electronic air detector 86 thatprevents infusion of air into the patient. The air detector 86 is ofultrasonic type and can detect air in amounts exceeding approximately 50micro liters traveling inside the infusion tubing 32. In one example,air detector 86 employs technology based on the difference of the speedof sound in liquid and in gaseous media. If an air bubble is detected,the pump 22′ is stopped almost instantaneously.

Console 82 may include one or more weight scales such as an electronicstrain gage and other means to periodically detect the weight of thecollected urine in chamber 52 and, if desired, the weight of theremaining hydration fluid in chamber 26. In the proposed embodiment, bag52 with collected urine and the bag 24 with hydration fluid 26 arehanging off the hooks 90 and 92 connected to the balance. The bags withfluids are suspended from the hooks and a system of levers translateforce to a scale such as strain gage 22′. The strain gage converts forceinto an electronic signal that can be read controller 34″. Suitableelectronic devices for accurately measuring weight of a suspended bagwith urine are available from Strain Measurement Devices, 130 ResearchParkway, Meriden, Conn., 06450. These devices include electronics andmechanical components necessary to accurately measure and monitor weightof containers with medical fluids such as one or two-liter plastic bagsof collected urine. For example, the overload proof single point loadcell model S300 and the model S215 load cell from Strain MeasurementDevices are particularly suited for scales, weighing bottles or bags inmedical instrumentation applications. Options and various specificationsand mounting configurations of these devices are available. These lowprofile single point sensors are intended for limited space applicationsrequiring accurate measurement of full-scale forces of 2, 4, and 12pounds-force. They can be used with a rigidly mounted platform or tomeasure tensile or compressive forces. A 10,000 Å wheatstone bridgeoffers low power consumption for extended battery life in portableproducts. Other examples of gravimetric scales used to balance medicalfluids using a controller controlling the rates of fluid flow from thepumps in response to the weight information can be found in U.S. Pat.Nos. 5,910,252; 4,132,644; 4,204,957; 4,923,598; and 4,728,433incorporated herein by this reference.

It is understood that there are many known ways in the art ofengineering to measure weight and convert it into computer inputs.Regardless of the implementation, the purpose of the weight measurementis to detect the increasing weight of the collected urine in the bag 52and to adjust the rate of infusion or hydration based on the rate ofurine flow.

Console 82 is also typically equipped with the user interface. Theinterface allows the user to set (dial in) the two main parameters oftherapy: the duration of hydration and the desired net fluid balance atthe end. The net fluid balance can be zero if no fluid gain or loss isdesired. Display indicators on the console show the current status oftherapy: the elapsed time 100 and the net fluid gain or loss 102.

The user interface may also include alarms 104. The alarms notify theuser of therapy events such as an empty fluid bag or a full collectionbag as detected by the weight scale. In one proposed embodiment, theurine is collected by gravity. If urine collection unexpectedly stopsfor any reason, the system will reduce and, if necessary, stop the IVinfusion of fluid and alarm the user. Alternatively, the console caninclude the second (urine) pump (see pump 70, FIG. 2) similar toinfusion pump 22. This configuration has an advantage of not dependingon the bag height for drainage and the capability to automatically flushthe catheter 14, FIG. 3 if it is occluded by temporarily reversing thepump flow direction.

FIG. 4 illustrates an algorithm that can be used by the controllersoftware of controller 34″ to execute the desired therapy. The algorithmis executed periodically based on a controller internal timer clock. Itis appreciated that the algorithm can be made more complex to improvethe performance and safety of the device. Controller 34″, FIG. 3 isprogrammed to determine the rate of change of the urine weight, steps110 and 112, FIG. 4 to calculate a desired infusion rate based on therate of change of the urine weight, step 114, and to adjust the infusionrate of the infusion pump 22, FIG. 3 based on the calculated desiredinfusion rate, step 116, FIG. 4.

So far, the subject invention has been described in connection with thebest mode now known to the applicant. The subject invention, however, isnot to be limited to these disclosed embodiments. Rather, the inventioncovers all of various modifications and equivalent arrangements includedwithin the spirit and scope of the appended claims. Particularly, theembodiments used to illustrate the invention use the weight of thecollected urine for balancing. It is understood that it is the volume ofthe urine that is clinically important but the weight of the urine isequivalent for any practical purpose. For the purpose of thisapplication, 100 grams of urine are the same as 100 ml of urine. It isbelieved at the time of the subject invention that measuring weight ismore practical than measuring volume and that the weight is often usedas a clinically acceptable substitute of volume of liquids that consistmostly of water. For practical purposes, the specific gravity (specificgravity of a substance is a comparison of its density to that of water)of urine and hydration fluids is the same as water. Those skilled in theart will realize that it is possible to measure volume directly using ameter which monitors the height of the column of the liquid in a vesselor by integrating the known volume of strokes of the pump over time. Theexact meter used does not change the subject invention in regard to thebalancing of urine output with hydration. Also, flow meter 36′, FIG. 5could be used to measure the urine output of patient P and a signalcorresponding to the flow rate provided to controller 38. Urine flowmeter 36′, FIG. 5 can be one of the devices disclosed in U.S. Pat. Nos.5,891,051; 5,176,148; 4,504,263; and 4,343,316 hereby incorporatedherein by this reference.

Also a medical device manufacturer, SFM Ltd., 14 Oholiav Street,Jerusalem, 94467, Israel manufactures and markets an electronic flowmeter suitable for use with this invention. According to themanufacturer SFM Ltd. the UREXACT 2000 System is an accurate electronicurine-measuring device that combines an innovative disposable collectionunit with a re-usable automatic electronic meter to provide preciseurine monitoring. The UREXACT 2000 is based on the ultrasonic method ofmeasuring fluid flow.

Thus, although specific features of the invention are shown in somedrawings and not in others, this is for convenience only as each featuremay be combined with any or all of the other features in accordance withthe invention. The words “including”, “comprising”, “having”, and “with”as used herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments. Other embodiments will occur to those skilled inthe art and are within the following claims.

In addition, any amendment presented during the prosecution of thepatent application for this patent is not a disclaimer of any claimelement presented in the application as filed: those skilled in the artcannot reasonably be expected to draft a claim that would literallyencompass all possible equivalents, many equivalents will beunforeseeable at the time of the amendment and are beyond a fairinterpretation of what is to be surrendered (if anything), the rationaleunderlying the amendment may bear no more than a tangential relation tomany equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for anyclaim element amended.

1. A fluid management system for a patient, the system comprising: aconsole for mounting on an IV pole, the console including an input forsetting a desired fluid balance for a set therapy duration; a firstattachment mechanism extending from the console for hanging a urinecollection chamber; a second attachment mechanism extending from theconsole for hanging a source of hydration fluid; a weighing subsystem inthe console responsive to the first attachment mechanism for weighingthe patient's urine output collected in the urine collection chamber andresponsive to the second attachment mechanism for weighing the source ofhydration fluid; an infusion pump integrated with the console andconfigured to pump hydration fluid from the source of hydration fluidinto the patient; and a controller in the console, responsive to the setdesired fluid balance, the set therapy duration, and the weighingsubsystem, the controller configured to: determine the patient's urineoutput based on the weight of the urine collection chamber, determinethe amount of fluid infused into the patient, and control the infusionpump to inject hydration fluid into the patient based on the set desiredfluid balance, the weight of the urine collection chamber, and theweight of the source of hydration fluid to achieve the desired fluidbalance during the set therapy duration.
 2. The system of claim 1 inwhich the console includes a display which displays the elapsed time ofthe therapy duration and the current fluid balance.
 3. The system ofclaim 1 further including means for indicating, on the console, when theurine collection chamber is empty.
 4. The system of claim 1 furtherincluding means for indicating, on the console, when the source ofhydration fluid is low on fluid.
 5. The system of claim 1 in which thecontroller is configured to determine the patient's urine output basedon the rate of change of the weight of the urine collection chamber,calculate a desired infusion rate based on the determined rate of changeof the weight of the urine collection chamber and the set desired fluidbalance, and control the infusion pump to hydrate the patient based atleast on the calculated desired infusion rate.
 6. A fluid managementsystem for a patient, the system comprising: a console including aninput for setting a desired fluid balance; a urine collection chamber; aweighing device for weighing the patient's urine output collected in theurine collection chamber; a source of hydration fluid; a pump associatedwith the console and configured to pump hydration fluid form the sourceof hydration fluid into the patient; and a controller in the consoleconfigured to: determine the patient's urine output based on the weightof the urine collection chamber, operate the pump, monitor the amount ofhydration fluid injected into the patient based, and control the pumpbased on the set desired fluid balance, the amount of hydration fluidinjected into the patient, and the determined patient urine output.
 7. Afluid management system for a patient, the system comprising: a consolefor mounting on an IV pole, the console including an input for setting adesired fluid balance; a first attachment mechanism extending from theconsole for handing a urine collection chamber; a weighing device in theconsole responsive to the first attachment mechanism for weighing thepatient's urine output collected in the urine collection chamber; acontrollable infusion pump integrated with the console and configured topump hydration fluid from a source of hydration fluid into the patientat a variable rate; and a controller in the console, responsive to theset desired fluid balance and the weighing device, the controllerconfigured to: determine the patient's urine output based on the rate ofchange of the weight of the urine collection chamber, calculate adesired infusion rate based on the determined rate of change of theweight of the urine collection chamber and the set desired fluidbalance, and control the infusion pump to hydrate the patient based atleast on the calculated desired infusion rate.
 8. A method of addressingcontrast induced nephropathy, the method comprising: injecting acontrast agent into a patient; imaging the patient; and includingdiuresis to drive any contrast agent through the patient's kidneys toreduce its toxic effects on the kidneys and prevent damage to thekidneys by: setting a desired fluid balance, collecting urine expelledby the patient in a urine collection bag, weighing the urine collectionbag, employing a pump to infuse the patient with fluid from a fluidsource, weighing the fluid source, and automatically adjusting the pumpbased on the weight of the urine collection bag and the weight of thefluid source and controlling the amount of fluid infused into thepatient based on the amount of urine expelled by the patient and the setdesired fluid balance.
 9. The method of claim 8 further including thestep of administering a diuretic to the patient.
 10. The method of claim8 in which collecting urine expelled by the patient includescatheterizing the patient.
 11. The method of claim 10 in whichcatheterizing the patient includes inserting a urinary catheter in theurinary tract of the patient.
 12. The method of claim 8 in whichweighing the urine collection bag includes providing an indication whena urine collection bag has reached its capacity.
 13. The method of claim8 in which weighing the fluid source includes providing an indicationwhen the fluid source is low on fluid.
 14. A method of addressingcontrast induced nephropathy for a patient who has had a contrast agentinjected into the patient, the method comprising: collecting urineexpelled by the patient; determining the amount of urine expelled by thepatient based on the collected urine; infusing the patient with fluidfrom a fluid source; determining the amount of fluid infused into thepatient; and inducing diuresis to dilute the concentration of anycontrast agent in the patient by automatically adjusting the amount offluid infused into the patient from the fluid source based on thedetermined amount of urine expelled by the patient to balance the amountof urine expelled by the patient with the amount of fluid infused intothe patient.
 15. A method of driving a toxin through a patient'skidneys, the method comprising: collecting urine expelled by thepatient; determining the amount of urine expelled by the patient basedon the collected urine; infusing the patient with fluid from a fluidsource; determining the amount of fluid infused into the patient; andinducing diuresis by automatically adjusting the amount of fluid infusedinto the patient from the fluid source based on the determined amount ofurine expelled by the patient to balance the amount of urine expelled bythe patient with the amount of fluid infused into the patient.
 16. Amethod of preventing kidney damage due to dehydration, the methodcomprising: collecting urine expelled by the patient; determining theamount of urine expelled by the patient based on the collected urine;infusing the patient with fluid from a fluid source; determining theamount of fluid infused into the patient; and maintaining the patient'shydration level by automatically adjusting the amount of fluid infusedinto the patient from the fluid source based on the determined amount ofurine expelled by the patient to balance the amount of urine expelled bythe patient with the amount of fluid infused into the patient;increasing the patient's level of hydration by infusing additional fluidbased on user settings over and above fluid infused to match thepatient's urine output.